A340587 - OEIS

%I #6 Jan 14 2021 15:02:59

%S 2,2,13,6,7,20,21,2,5,3,29,30,34,38,39,40,12,43,44,2,7,51,14,54,5,57,

%T 15,60,61,62,2,66,67,68,69,17,72,73,74,75,18,78,79,3,19,84,85,86,87,6,

%U 20,2,92,93,94,95,21,98,10,102,22,105,106,107,108,109,23,112

%N a(n) is the least root of A340586(n).

%F a(n) = A025478(A340586(n)).

%e a(1) = 2: A340586(1) = 4 = 2^2,

%e a(2) = 2: A340586(2) = 16 = 2^4,

%e a(3) = 13: A340586(3) = 169 = 13^2.

%o (PARI) a340587(limit)={my(p2=999, p1=2, n2=1, n1=4); for(n=5, limit, my(p0=ispower(n)); if(p0>1, if(p2+p0==4, print1(round(n1^(1/p1)), ", ")); n2=n1; n1=n; p2=p1; p1=p0))};

%o a340587(13000)

%Y Cf. A025478, A340586, A340641.

%K nonn

%O 1,1

%A _Hugo Pfoertner_, Jan 14 2021